Active oxygens produced by various cells and tissues such as leukocytes have recently received increased attention as new mediators. The active oxygen includes superoxide anions (.O.sub.2.sup.--), hydrogen peroxides (H.sub.2 O.sub.2), hydroxy radicals (.OH.sup.--), and singlet oxygens (.sup.1 O.sub.2), and in a wider sense, it includes peroxy radicals (LOO.), alkoxy radicals (LO.), and lipoperoxides (LOOH).
The active oxygen is a self-defensive factor, and is a tissue disorder factor as well. It has been clarified that tissue disorder attributable to excessive production of active oxygen causes autoimmune diseases, inflammatory diseases, circulatory diseases, and gastrointestinal diseases.
Therefore, it is expected that a compound which contributes to inhibition of the production of active oxygens, or trapping of active oxygens should be useful as a pharmaceutical.
While there have been so far developed various pharmaceuticals which inhibit production of active oxygens, or trap active oxygens, no satisfactory pharmaceuticals have been actually developed.